With practice, each of us can refine our perceptual skills. We can learn to see object features more clearly, hear the difference between sounds more easily, and discern flavors and smells with greater acuity. This ability to improve our perception – a process termed perceptual learning – supports a wide variety of complex, real-world behaviors, leaving its mark all around us— the wine expert’s refined palate, the artist’s keen eye, and the musician’s tuned ear are all the direct result of perceptual learning. In addition to enhancing everyday skills, perceptual learning also holds potential as a clinical intervention to alleviate symptoms of schizophrenia and dyslexia, and to improve vision and hearing in the elderly. The broad applicability of perceptual learning, and the promise it holds for both the restoration and augmentation of sensory function makes it of vital interest to determine how perceptual learning is implemented in the brain. We aim to address this issue by leveraging recent advances in optical, genetic, molecular, and wireless technologies to monitor and manipulate neural activity in behaving animals during perceptual learning.
Role of orbitofrontal cortex in perceptual learning
Our recent work suggests that the top-down networks that modulate auditory cortical activity are strengthened during perceptual training. Multiple lines of evidence suggest the orbitofrontal cortex (OFC) may be a key node in this process. To explore this possibility, we are using in vivo electrophysiology and fiber photometry to monitor OFC activity in freely-moving Mongolian gerbils as they train and improve on sound detection and discrimination tasks. We couple these experiments with pharmacological and chemogenetic manipulations of OFC activity to assess downstream effects on auditory coding and behavior. Finally, we plan to employ wireless optogenetics to simultaneously measure and manipulate activity in a cell-type specific and temporally precise manner.
Neural pathways supporting auditory cortical modulation
While top-down networks shape neural activity in the ascending auditory pathway, and guide perceptual learning, the specific pathways and connections involved remain unknown. We are leveraging intersectional viral approaches and confocal microscopy to establish the top-down inputs to the gerbil auditory system with the goal of identifying layer and cell-type specific targets. We also use these same approaches, along with in vivo single unit recordings, to explore the contribution of subcortical auditory structures, like the inferior colliculus, to learning-related cortical plasticity.
Neuromodulatory mechanisms of perceptual learning
A substantial body of literature indicates that neuromodulators, such as acetylcholine, noradrenaline, and dopamine, are involved in associative learning and cortical plasticity. While many of these same neuromodulatory systems are also likely to play an active role in perceptual learning, many details remain uncertain, including the specific neuromodulators involved, their sites of action, and how different modulatory systems work synergistically to enable training-based improvements in cortical and perceptual sensitivity. To address these issues, we are using fiber photometry and novel genetically-encoded biosensors to establish the temporal dynamics of neuromodulator release during perceptual learning. We are also using targeted pharmacological manipulations to determine whether the activation or blockade of specific receptor subtypes facilitates or attenuates learning.